netdev - Re: [PATCH net-next 0/5] virtio-net: support dynamic coalescing moderation

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Message-ID: <CACGkMEshFckmtY3RyNYiEATFkDkCvQSMWq1-3LwbM2gVgqPxVw@mail.gmail.com>
Date: Fri, 13 Oct 2023 09:53:53 +0800
From: Jason Wang <jasowang@...hat.com>
To: Heng Qi <hengqi@...ux.alibaba.com>
Cc: "Michael S. Tsirkin" <mst@...hat.com>, netdev@...r.kernel.org, 
	virtualization@...ts.linux-foundation.org, 
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Eric Dumazet <edumazet@...gle.com>, 
	"David S. Miller" <davem@...emloft.net>, Paolo Abeni <pabeni@...hat.com>, 
	Jesper Dangaard Brouer <hawk@...nel.org>, John Fastabend <john.fastabend@...il.com>, 
	Alexei Starovoitov <ast@...nel.org>, Jakub Kicinski <kuba@...nel.org>, Simon Horman <horms@...nel.org>, 
	"Liu, Yujie" <yujie.liu@...el.com>
Subject: Re: [PATCH net-next 0/5] virtio-net: support dynamic coalescing moderation

On Thu, Oct 12, 2023 at 4:29 PM Jason Wang <jasowang@...hat.com> wrote:
>
> On Thu, Oct 12, 2023 at 3:44 PM Heng Qi <hengqi@...ux.alibaba.com> wrote:
> >
> > Now, virtio-net already supports per-queue moderation parameter
> > setting. Based on this, we use the netdim library of linux to support
> > dynamic coalescing moderation for virtio-net.
> >
> > Due to hardware scheduling issues, we only tested rx dim.
>
> Do you have PPS numbers? And TX numbers are also important as the
> throughput could be misleading due to various reasons.

Another consideration:

We currently have two TX mode, NAPI by default, and orphan. Simple
pktgen test shows NAPI can only achieve 30% of orphan. So we need to
make sure:

1) dim helps for NAPI, and if NAPI can compete with orphan, we can
drop the orphan code completely which is a great release and
simplification of the codes. And it means we can have BQL, and other
good stuff on top easily.
2) dim doesn't cause regression for orphan

Thanks

>
> Thanks
>
> >
> > @Test env
> > rxq0 has affinity to cpu0.
> >
> > @Test cmd
> > client: taskset -c 0 sockperf tp -i ${IP} -t 30 --tcp -m ${msg_size}
> > server: taskset -c 0 sockperf sr --tcp
> >
> > @Test res
> > The second column is the ratio of the result returned by client
> > when rx dim is enabled to the result returned by client when
> > rx dim is disabled.
> >         --------------------------------------
> >         | msg_size |  rx_dim=on / rx_dim=off |
> >         --------------------------------------
> >         |   14B    |         + 3%            |
> >         --------------------------------------
> >         |   100B   |         + 16%           |
> >         --------------------------------------
> >         |   500B   |         + 25%           |
> >         --------------------------------------
> >         |   1400B  |         + 28%           |
> >         --------------------------------------
> >         |   2048B  |         + 22%           |
> >         --------------------------------------
> >         |   4096B  |         + 5%            |
> >         --------------------------------------
> >
> > ---
> > This patch set was part of the previous netdim patch set[1].
> > [1] was split into a merged bugfix set[2] and the current set.
> > The previous relevant commentators have been Cced.
> >
> > [1] https://lore.kernel.org/all/20230811065512.22190-1-hengqi@linux.alibaba.com/
> > [2] https://lore.kernel.org/all/cover.1696745452.git.hengqi@linux.alibaba.com/
> >
> > Heng Qi (5):
> >   virtio-net: returns whether napi is complete
> >   virtio-net: separate rx/tx coalescing moderation cmds
> >   virtio-net: extract virtqueue coalescig cmd for reuse
> >   virtio-net: support rx netdim
> >   virtio-net: support tx netdim
> >
> >  drivers/net/virtio_net.c | 394 ++++++++++++++++++++++++++++++++-------
> >  1 file changed, 322 insertions(+), 72 deletions(-)
> >
> > --
> > 2.19.1.6.gb485710b
> >
> >